Detergent purification



United States Patent ice;

DETERGENT PURIFICATION 7 Vincent A. Sullivan, Jr., Lyons, and Zdzislaw Joseph Ptasinski, Chicago, 'Ill., assignors to The Stepan Chemical Company, Chicago, Ill., a corporation of Illinois No Drawing. Application February 18, use,

Serial-No. 337,646

15 Claims. (Cl. 252- 156) 'Our invention relates to novel and unique synthetic detergent compositions and an improved method for their separatiomand more particularly, to improved compositions of the'type characterized by the presence therein of water-soluble anionic sulf onated detergents in the liquid state, and the method of preparing'the same.

As is well known, the ever increasing need for improved liquid detergent compositions has resulted in the expenditure of a substantial amount of research time and attention. The particularly complicated physical and chemical phenomena here involved have, however, added a great deal of confusion'to the. art and have given-rise to a :great plurality of conflicting theories and comcepts. The complexity of the overall problem is readily appreciated when one considers the fact that the phenomena here involved include suspension, interfacial tension, micellar structure, dispersion, emulsion, foam stability and the like. w

As is pointed out in the United States Patent No. 2,607,740, issued August 19, 1952, to Peter T. Vitale and Ralph Spencer Leonard, and assigned to Colgate- Palmolive-Feetv Company, recently synthetic detergents of a type known as organic sulfonates have been developed, and the detergents of this characteristic type have been 'found 'to have certain properties which render them much more suitable than ordinary soaps for certain uses. Since these detergents have m'any properties substantially different from the properties of soaps and particularly, since they behave in a substantially diiferent manner in aqueous solution, for example, by the non-formation of insoluble precipitates in hard, water, the "improvement or alteration of the general behavior characteristics of these detergents has opened up an entirely new'fi'eld of research. One of such fields of research involves certain attempts to prepare these detergents substantially 'free from 'impurities, and particularly inorganic salt impurities. The presence of such 'salts'often adversely affects "such properties as the cloud point (in liquid compositions) and also has an adver'seeifect upon the'ove'rall cleansing properties. It is highly desirable to'have detergent compositions of this particular type which possess excellent clarity in combination with excellent detersive efliciency; and this particular combination of properties is'of very appreciable importance in connection with consumer appeal for home use, as Well as for industrial use.

Although detergents of this type can be, and are currently being, packaged and sold in dry particular form, the presence of such salt impurities therein-tends to create additional precipitate deposits during use. Also, certain features of this type ofpackaging leave something to be desired; and there has developed a very great demand on the part of home users as well as industrial users for suitable synthetic detergent compositions in liquid form. Those skilled in the ar-t, however, recognize fully that a rather substantial number of critical considerations are involvedin the formulation of a suitable liquid detergent composition, and certain of the-more important of'these particular considerations .are set forth at some length in said U. S. Patent No. 2,607,740, and need not be elab- 2,768,957 Patented "oat. so, 1 956 orat'ed upon at this point 'in this disclosure. The main point here "involved is that a commercially suitable cont-- positionmust necssarily have suitable propertiesin-con n'ection'with the critical'considerations, such as viscosity; selective solvent/cloud point, foaming, grease eniulsifi-i cation, soilremoval, adequate concentration and use of irritants'in the composition. 'In generah'tlie'liquid deter gent compositions heretofore known have lefit something to be'desired in connection with one or more'of the "fore? going critical considerations, because of the presence thereinof the salt impurities just mentioned.

The purification problem here involved inay best be analyzed by'a careful study'of the procedure employed for preparing such detergents. In general, thefirst'step involves sulfonation of a suitable compound such as dodecyl benzene toyield a crudemixture of-dodecyl benzene sulfonic acid and the sulfonating agent. 'Any suit- C lt 25 i I an a m The product shown in each case is a true sulfonic acid having a C--SO3H group and this is the predominant product obtained using vigorous anhydrous reaction conditions. Actually, at least some sulfate (i, e. COSO3H) is usually formed also. The conditions involve minimum reaction temperatures (i. e. not above 190 -1 19 F. if possible) to avoid discoloration and a substantial excess of the sulfonating agent to insure substantially complete sulfonati-on of the hydrocarbon (which is by comparison relatively expensive). I

The next step involves washing of the crude sulfonated productwith water to remove the excess sulfonating agent (which is effectively converted into HzSQ4 by the washing process so as to remove the bulk of the excess in the form of a concentrated (80% solutionof H2504. In orderto avoid excessive loss of the 'sulfonated hydrocarbon (and to obtain a concentrated H2804 solution) only a, relatively small amount of Water'is used. Thedodeeyl benzenesulfenrc acid, however, hasaselective retention or absorption with respect to the sulfuric acid and it is impossible to remove all of the sulfuric acid from the sulfonic acid by this washing. The resulting washed crude sulfonic acid product has a composition of about 88% dodecyl benzene sulfonic acid, 7% sulfuric acid, 4% water and 1% dodecyl benzene. Heretofore, no practical method had been devised for removing -a greaterproportion of the sulfuric acid. I U

Thehext step involves neutralization of the washed crude s'ulfonic acid; and this may be done by the ;use of inorganic bases such as alkali metal or ammonium hydroxide or by the use of organic bases such as the ethanolamines. Here again, low temperatures of not more than about -1 10 is used to avoid discoloration. If,- for example, sodium hydroxide is used, the resulting neutnali'z ed sodium dodecyl benzene sulfonate contains about 12% NazSO4. (As used herein the terms percent and parts means percent and parts by weight, unless otherwise designated.) Other inorganic bases cause the formation of the corresponding amounts of their-sulfate salts. It will thus be seen that the presence of'such inorganic sulfate salts in the final neutralized sulfonated product is inherent and unavoidable.

As those skilled in the art will readily appreciate, the rather substantial amount ofthe inorganic salt impurity in such compositions greatly impairs their use as chemical intermediates for other reactions and also as ingredients suitable for admixture with other ingredients to form detergent compositions, for example. Moreover, the inorganic sulfate impurity has solubility characteristics that are substantially different from those of the organic sulfonate and the use of selective solvents in liquid detergent compositions containing these sulfonated detergents is further complicated. It will also be appreciated that the sulfonated detergent .per se is generally looked upon as the sulfonic acid, or the sulfonic acid anion properly speaking, but it is necessary as a practical matter to neutralize the sulfonic acid to form the salt thereof for use in detergent compositions. As has been pointed out, however, there was heretofore no known practical method of separating the sulfate anion (neutralized or unneutralized) from the sulfonate; and the inherent presence of these substantial amounts of sulfate anion is not at all desirable.

Ifan organic base, such as triethanolamine, is used to neutralize the crude washed sulfonated detergent then triethanolamine sulfate impurities are formed. Such organic sulfate impurities are not as radically different from the solubility characteristics of the sulfonate as are the inorganic sulfates. For this reason, the inorganic base neutralized sulfonated detergents have been replaced by those neutralized by organic bases in many uses. The organic base neutralized sulfonated detergents also leave much to be desired, however, since their use may involve the use of a sulfate having better solubility but nevertheless a sulfate which introduces undesirable sulfate anions into the system. Also, the organic bases such as the alkylolamines are relatively expensive and the alkylol amine employed in neutralizing the sulfuric acid is for all intents and purposes lost or wasted as far as detersive efiiciency is concerned. It is, therefore, an important object of our invention to provide an improved method of producing low-sulfate content anionic sulfonated detergents, and the improved detergents resulting therefrom.

Itis a further object of our invention to provide an improved method of treating a composition comprising essentially 100 parts of Water-soluble salt of anionic sulfona-ted detergent having a long aliphatic chain of 8 to '22 carbon atoms, and 1 to 20 parts of inorganic sulfate salt whereby the amount of inorganic sulfate salt therein may be reduced to a predetermined amount x, within the range of -1 part, which comprises intimately admixing the composition with -50 weight percent of amide derivative selected from the group consisting of (1) dialkylolamide having the formula:

ROON

RI! wherein R-CO- is a fatty acyl radical of to 14 carbon atoms, and R and R" are hydroxyalkyl groups of up to 5 carbon atoms each; and (2) polyalkoxyalkylolamide condensate of 2 to 5 mols of alkylene oxide having 2 to 3 carbon atoms with 1 mol of higher fatty acid amide having the formula:

All

wherein R-CO-- is a fatty acyl radical of 10 to 14 carbon atoms, and A and A" are each selected from the group consisting of H and hydroxyalkyl radicals of up to 5 carbon atoms each and each having 1 to 2 hydroxy groups with none of the carbon atoms having more than one hydroxy group attached thereto; and /2 to 5 times its weight of a one phase solvent system of water admixed with low molecular weight solvents of the class consisting of alcohols, ketones, esters and ethers in an amount sufficient to reduce the total solubility of the system for their organic sulfate salt to x, then agitating the admixture for a time suflicient to completely dissolve the sulfonated detergent and to effectively coagulate the undissolved inorganic sulfatesalt particles therein, and then filtering the admixture to remove the coagulated salt particles therein.

It is another object of our invention to provide an improved concentrated liquid detergent composition consisting essentially of at least 25 weight percent of Water-soluble salt of anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms and 5-50 weight percent of the detergent of amide derivative selected from the group consisting of (1) dialkylolamide having the formula:

wherein RCO- is a fatty acyl radical of 10 to 14 carbon atoms, and R and R are hydroxyalkyl groups of up to 5 carbon atoms each; and (2) 'polyalkoxyalkylolamide condensate of 2 to 5 mols of alkylene oxide having 2 to 3 carbon atoms with 1 mol of higher fatty acid amide having the formula:

All

wherein R-CO- is a fatty acyl radical of 10 to 14 carbon atoms, and A and A" are each selected from the group consisting of H and hydroxyalkyl radicals of up to 5 carbon atoms each and each having 1 to 2 hydroxy groups with none of the carbon atoms having more than one hydroxy group attached thereto; in a selective liquid solvent therefor; and less than 1 weight percent of the sulfonated detergent of inorganic sulfate salt.

Other objects, features and advantages will become apparent to those skilled in the art from the following detailed disclosure of preferred embodiments of our invention.

A basic aspect of our invention consists in a method of treating a composition comprising essentially watersoluble salt of anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and 1 to 20 weight percent thereof of inorganic sulfate salt, that comprises intimately admixing the composition with substantially an equal weight of ethanol and water in volume ratio of 50:50 to 60:40 and 25% of dialkylolamide having the formula:

wherein R-CO- is a fatty acyl radical of 10 to 14 carbon atoms, and R and R" are hydroxyalkyl groups of up to 5 carbon atoms each; heating the admixture'to from F. to boiling temperature for a time suflicient to completely dissolve the sulfonated detergent and to effectively coagulate the undissolved inorganic sulfate salt particles therein, and then filtering the admixture to remove the coagulated salt particles therein.

The anionic sulfonated detergents which we may employ in the practice of our invention are a well known class of compounds, as is pointed out in said Patent No.

era-ape? 2,5071740. These detergents ar'eiallmade procedures comparable to that hereinbefore .described. The sulfonation may take place usinga variety of suitable source materials each having an aliphatic chain of about 8 to about 22. The sulfonation may takeplace with higher fatty alcohols, so as to obtain, for example, lauryl sulfonate and preferably Cm-Cm alkyl sulfonates. Most preferably, however, alkyl aryl compounds are used. The aromatic or alkyl aryl sulfonate detergents are well known inthe art. They may be mononuclear or polynuclear in structure. More particularly thearomatic nucleus may be derived from benzene, toluene, xylene, phenol, cresols, naphthalene, etc. The alkyl substituent on the aromatic nucleus may vary widely, as long as the desired detergent power of the active ingredient is preserved. While .thenurnber of sulfonic acid groups present on 'the nucleus may vary it is usual to have one such group present in order to preserve as much as possible a balance between the hydrophilic and hydrophobic vportions of the molecule.

More specific examples ofsuitable alkyl aromatic sulfonate detergents are the higher alkyl aromatic sulfonates. The higher alkyl substituent on the aromatic nucleus may be branched or straight-chain in structure; it comprises moreover such groups as decyl, dodecyl, keryl, pentadecyl, hexadecyl, mixed long-chain alkyls derived from long-chain fatty materials, cracked paraffin wax olefins, polymers of lower monoolefins, etc. Preferred examples of this class are the higher alkyl mononuclear aryl sulfonates wherein the alkyl group is about 8 to about 22, and preferably about 12 to 18 carbon atoms. -More particularly, it is preferred-to use the higher alkyl benzene sulfonates wherein the higher alkyl group is about 12 to 16 carbon atoms. For example, propylene may be polymerized to the tetramer and condensed with benzene in the presence of a Friedel-Crafts catalyst to yield essentially the dodecyl benzene derivative which is suitable forsulfonation to the desired sulfonate compounds.

The above mentioned anionic detergents are used or ultimately obtained in the instant invention in the form of their. water-soluble salts, which salts include the ammonium, alkali metal and alkaline earth metal salts,

obtained by neutralization with an inorganic-base, and the alkylol amine salts normally obtained by neutralization with the corresponding organic base. Such salts include the lower three alkali metals (lithium, sodium and potassium, which are the only commercially significant alkali metal salts) the ammonium salts, and the triethanol amine salts. Although in certain instances, the alkylol amine salts have been found to be particularly preferable (e. g., the monoethanolamine, diethanolamine, triethanolamine salts and mixtures thereof have been found to be particularly useful); however, 'we have also found that the alkali metal salts, particularly the alkali metal alkyl benzene sulfonates and higher alkyl sulfates, are advantageous in many respects including economic aspects and are preferred for use in the instant invention. The problem here solved is that of obtaining these sulfonate salts in a substantially sulfate-free condition.

As also explained, the procedure for the preparation of the sulfonated detergent inherently results in the incorporation therein of the sulfate (anion); and subsequent neutralization merely results in the formation of the corresponding sulfate salt as an impurity. No practical method was heretofore known for avoiding the presence of the neutralized or unneutralized sulfate in such sulfonated detergent compositions.

The details of the sulfonation process per se are old and well known to those skilled in the art, and need not be discussed at length herein. The formation of a sulfonated anionic detergent is, likewise, a well known 'procedure. A suitable sulfonatable detergent source material (having a long aliphatic chain of about Cit-C22) which may be a hydrocarbon (e. g. dodecyl benzene), an al- 6 v col ;ol.('e. g. l-auryl alcohol), fan ester-alcohol (e.:=g. lauroyl diglyceri'de'), etc, isIe'acte'd with one .of the sulfonating agents hereinbefore described. Most preferably thes'ource material is a Clo-C16 .alkyl benzene.

The result of the sulfonating reaction is a member of the well known class of detergents called anionic sulfonated detergents; and such sulfonated compounds by virtue of their retentive powers for the sulfonating agent inherently contain substantially quantities of the same, even after washing or any other known refining treatrnent. After washing, these sulfonated detergents inherently contain from about 3% to about 10% of the sulfonating agent, depending to some extent upon the particular agent. (Using sulfur trioxide it is possible to obtain a lower percent retained :than by using sulfuric acid.) Neutralization of the washed sulfonated product; results in a neutralized product which maycontain from about 5% to about 20% of the neutralized sulfonating agent as the sulfate salt of the neutralizing base. Again, the neutralized sulfate-containing product is well known in the art.

Our invention contemplates the use of-this well known neutralized product as a starting material, when such is neutralized with an inorganic base; and this material is here defined as .a composition comprising essentially water-soluble salt of anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and 5 to 20 weight percent thereof of inorganic sulfate salt. The-inventi0nalso contemplates the use of such a composition containing as little as 1 weight percent of the sulfate, which composition is itself new but which can be obtained by practicing this invention so as to carry out an initial reduction in sulfate content fror'nvthe minimum of about 5% (heretofore obtainable) to as low as 1%.

The nature of our invention may probably best be demonstrated by carrying out a specific process embodying the invention as follows:

A starting material was provided that was a composition comprising essentially water-solub1e salt of anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and l to 20 weight percent thereof of an inorganic sulfate salt, and more specifically, sodium dodecyl benzene sulfonate containing 12% sodium sulfate (whose preparation was described in detail hereinbefore). The composition was admixed with an equal weight (and, preferably, /2--1 /2 times the composition weight) of 55 volumes of ethanol and 45 volumes of water, which effectively reduces the sulfate concentration to 6% in the admixture. Ethanolzwater volume ratios of 60:40 to 50:50 may be used to obtain admixtures which dissolve about 0.2-0.4% sulfate. This ethanolwater solvent (system) is capable of fully dissolving the sulfonate detergent, but his capable of actually dissolving only about 0.3% sulfate, which means that 5.7% sulfate is excluded from the solvent phase and a twophase system involving a second dispersed sulfate phase is formed. As will be appreciated, the neutralization with sodium hydroxide was carried out at temperatures not in excess of l00ll0 F. and the subsequent solvent addition has served to cool the admixture substantially below the neutralization temperatures. Under such conditions, the second dispersed sulfate phase is barely apparent, if at all, since we have found that the dispersed sulfate particles are extremely minute in character. In fact, it might be expected that the presence of the sulfonate in solution would create a selective solvent system for all of the sulfate; instead, we believe that the sulfonate contributes materially to the almost infinitely fine dispersion here obtained but does not actually retain the sulfate in solution (in excess of the 0.3%).

There is no known way of separating this fine sulfatedispersed phase from the solvent phase so as to obtain a one-phase (solvent-phase) system. As such, the dispersed sulfate cannot be filtered out or removed by any would build up into crystals of appreciable size.

other known practical means. We use the term .disperseds ulfate to describe the undissolved sulfate advisedly because we have found that the sulfate is, in fact, not soluble in this system and must, therefore, be undissolved and dispersed therein. Others may not have appreciated this fact, and considered the sulfate to be dissolved, but with or without the knowledge that the sulfate cannot be dissolved in true solution there is still no apparent method of removing the (undissolved) sulfate.

The key to the sulfate removal, we have found, isthe addition of a certain type of non-ionic amide derivative in conjunction with the solvent addition, and then agitating the mixture so as to effect complete solution of the sulfonateddetergent and also to effect coagulation of the inorganic sulfate present. For example, weight percent of the detergent of lauroyl diethanolamide was added to the above described admixture and was thoroughly agitated therewith for about /2 hour, and it was found that noticeable precipitation and/or coagulation had taken place in connection with the sulfate particles. The removal of thesecoagulated particles by filtration, using a standard grade filter cloth in a filter press is then accomplished without difiiculty and the filtered product was found to have a sodium sulfate content of trace proportions (i. e., about 0.1% or less).

When the foregoing procedure was repeated using in this case 59 volumes of ethanol and 41 volumes of water, not even a trace proportion of sodium sulfate was detectable in the final product.

Although it is not desired to limit the invention to any particular theory, we believe that the unusual result here obtained may be explained as follows:

The addition of the ethanol-water solvent to the sulfonate having dissolved therein the sulfate creates a system wherein only a small part of the sulfate is soluble and the precipitate or separate from the solvent phase. The initially precipitated or separated particles are almost colloidal in size but under ordinary conditions The sulfonate in this system, however, prevents this build-up perhaps by forming a protective film on the surface of these particles as soon as they take form. The result is what appears to be a true solution, but which has a relatively high cloud point. In our invention, however, we add an additional ingredient to this system for the purpose of increasing the solubilizing or coagulating activity of the solvent phase, presumably so that this protective film may be removed or otherwise rendered ineffective and coagulation of the minute particles may take place to form a preferable precipitate.

It will be seen that an important additive which is used in the practice of our invention is an amide derivative. Actually, this amide derivative is classifiable into two types of different, but related monionic amide structures. The first of these structures is a dialkylolamide and the second of these amides is referred to as a polyalkoxyalkylolamide condensate. Both of these amides contain a characteristic higher fatty acid amide grouping, but the former of these two groups of amides is preferred for use in the instant invention, since the compounds of this former group or class are particularly superior with respect to avoidance of a tendency toward cloudiness and the effective coagulation of the sulfate.

The dialkylolamides which may be used in the practice of the instant invention have been described in detail in said U. S. Patent No. 2,607,740, and these compounds are characterized by their weakly polar nature and may be represented by the following formula:

wherein RCO- represents a fatty acyl radical of 10-14 carbon atoms, and R and R" may be the same or different, each being a lower hydroxyalkyl group of pref- 7 molecular weight.

the diethanolamide compounds and the additives possessing a fatty acyl radical of 12-14 carbon atoms.

These dialkylolamides may be prepared in any suitable manner and numerous processes for their production are well known in the art. A convenient and economical mode of synthesis involves the condensation of the higher fatty acylating compounds (e. g. lauric acid, lauric acid halide, etc.) with a suitable amino compound to produce a reaction product having the desired amide structure.

The higher fatty acylating substances may be derived from pure, impure or commercial grades of capric, lauric or myristic acids and the like. acids may be produced from fatty oils, fats, greases, and other natural sources or be of synthetic origin as derived from the oxidation of hydrocarbons. According to its origin and the degree and manner of purification, capric, lauric and myristic acids may be commonly admixed or associated with other fatty acids of higher and lower It is within the scope of the invention that the capryl, lauroyl and myristoyl compounds may be associated with other fatty substances and the like provided the character and amount of such other materials are not sufficient to substantially neutralize or materially affect the enhancing power of the additives in the relationship set forth. Thus, there may be suitably employed for the preparation of the dialkylolamide additives the commercially pure capric, lauric and myristic acids having a concentration of such acids of about and above. A typical composition of commercially pure lauric acid may be 90% lauric acid, 9% myristic acid, 1% unsaturated acids, trace capric acid. Another suitable fatty acid mixture is topped coconut oil fatty acids produced by the removal of a low-boiling fraction, e. g.

the dialkylolamines may be utilized in pure, impure, or

commercial form.

According to the circumstances of manufacture of the dialkylolamide, it may be chemically and/or physically associated with other materials such as soap, free alkylolamine, piperazine type derivatives, etc. The presence of varying amounts of such materials and the like in admixture with dialkylolamide is contemplated within the scope of the present invention, provided the same are not significant enough to materially neutralize or substantially adversely affect the desired improvements to be accomplished with the combination of the anionic detergent and the dialkylolamide additive.

It is a particular feature of this invention that the reaction product of the higher fatty acylating substance and the 'dialkylolamine comprising the desired dialkylolamide and other derivatives as produced under certain conditions may be utilized with marked success as additives in the novel compositions of the present invention. More particularly, the product is to be produced by the condensation of the suitable higher fatty acids or their equivalent with an equivalent or an excess of dialkylolamine, the molar ratio being from about 1:1 to about 1:10 but preferably up to about 1:5 and usually from about 1:2 to about 1:3, at from about C. to about 200 C., and preferably from about C. to 180 C., and achieving More particularly, these a reaction mixture equilibrium comprising an .efiective amount of the dialkylolamide. With the fatty acids, an excess of dialkylolamine will usually be used, preferably upto about 3:1. Using fatty acids or anhydrides illustratively as reactants, as the water is distilled off or otherwise removed during the reaction, the acid number falls indicating formation of amides. The reaction is to be continued until the desired amount of water has been removed, e. g. not substantially in excess of 15% acid or soap and preferably up to about 10% as determined by the acid value resulting from titration of the reaction mixture with potassium hydroxide. With the use of methyl esters and the like as reactants, the amount of alcohol liberated is an index of completion of the reaction. In the case of the acid chlorides and the like as reactants, formation of chloride ion or its equivalent may be determined also. This condensation reaction between the higher fatty acids and the alkylolamines or their equivalents is highly complex and produces a variety of products in addition to the desired di-alkylolamide. Accordingly, it is necessary to achieve an equilibrium of the reaction mixture containing an effective proportion of the dialkylolamide. This equilibrium may be achieved usually by permitting the reaction mixture tocool relatively slowly or maintaining the reaction mixture at slightly elevated temperatures for a sufiicient period of time. The optimum equilibrium of the reaction mixture however achieved may be determined by routine tests such as hereinafter set forth wherein the novel liquid detergent compositions are subjected to practical washing operations. Atypical suitable reaction mixture cited for illustrative purposes and resulting from the condensation of commercially distilled laun'c acid in 90% purity and commercial diethanolamine contains the following components on a solids basis: diethanolamide about 65%, diethanolamine soap about 10%, free amine, diethanolpiperazine and minor amounts of possibly other substances totaling 25%. The reaction product may contain usually minor amounts of water also, e. g.' about 'We may also use in the practice of our invention polyalkoxyalkylolamide condensate of 2 to 5 mols of alkylene oxide having 2 to 3 carbon atoms with 1 mol of higher fatty acid amide having the formula:

wherein RCO is a fatty acyl radical of to '14 carbon atoms, and A and A" are each selectedfrom the group consisting of H and hydroxyalkyl radicals of up to 5 carbon atoms each and each having 1m 2 hydroxy groups with none of the carbon atoms having more than one hydroxy group attached thereto. 'It will thus be seen that this ingredient includes alkylene oxide condensates of monoalkylol and dialkylolamides.

The dialkylolamides which may be used in the practice of the instant invention have just been described in detail. The compounds of the monoalkylolamide class which we may use in connection with the instant invention have been substantially described in United States Patent No. 2,382,737, issued August 28, 1945, to Albert 'S..Richardson, and assigned to The Procter and Gamble Company. In general, these compounds may have theformula:

wherein RCO is a fatty acylradical of about 1'0-14 carbon atoms, and A is a hydroxyalkyl radical of upto about 5 carbon atoms and having 1 to 2 hydroxy groups with none of the carbon atoms having more than one hydroxy group attached thereto. Examples include:

wherein R is decyl, llauryl, .myristyl andkeryl, and mix. tures of such compounds. Any of the alkylol ,groups disclosed in connection with the .dialkylolamide may, of course, be used; and it is also apparent that those dihydroxy groups (such as the 2,3 dihydroxy propyl group) may, of course, be present in the dialkylolamide hereinbefore disclosed. The method of preparing .the monoalkylolamides are disclosed in detail in said U. S. Patent No. 2,383,737 and need not be discussed in further detail herein.

The invention contemplates the use.of the alkyleneoxide condensates of these monoand di-alkylol amides, using alkylene oxides having 2 to 3 carbon atoms, i. e., ethylene oxide and propylene oxide and mixtures thereof. The invention also contemplates the use of the amide, RCO-NH2, wherein RCO- is the fatty acyl radical hereiubefore described. Since it cannotalways be ascertaincd with definiteness just where the polyalkoxide addition takes place in the amide molecule, the compounds are referred to as the condensates of 2 to 5 mols of alkylene oxide with 1 mol of the amide. It is, however, generally understood that the alkylene oxide condensation chain (i. e. the polyalkoxyalkylol group) attaches at the amide hydrogen, if present, so as to form --N(Alk--O H wherein y is 2 to 5; or is attached at the hydroxy hydrogen of an alkylol group, so as to form for example. It is also understood that the two or more mols of alkylene oxide here used will attach themselves to the amide molecule to form a given chainhaving two or more alkylene oxide units therein. Most preferably, however, the resulting condensate has a total of at least about 3 alkylene oxide units therein, which alkylene oxide units include those contained in the one or two alkylol groups attached to the amide initially as well as the alkylene oxide units added by condensation. It will thus be seen that on the basis of this minimum, the following condensates may be used:

(1) Lauroyl amide plus 3 mols ethylene oxide (2) Lauroyl monoisopropanol amide plus 2 mols of ethylene oxide (.3) Lauroyl diethanolamide plus 1 mol of ethylene oxide.

As wehavepreviously mentioned, however, it is preferable to condense at least about 2 mols of the alkoxide'with 1 mol of amide, except in the case of the dialkylolamides, where 1 mol of alkoxide yields a superior product.

.In general, the reaction conditions for alkylene oxide condensation are Well .known to those in the art, and a detailed discussion herein is not necessary. A typical example is as follows: 1

Lauroyl diethanolamide was first prepared by reacting 1 mol of .lauric acid with 2.0 mol of diethanolamine at -200" C. for about 4 hours with continuous distillation and removal of water. The resulting lauroyl diethanolamide was heated with one molar equivalent of ethylene oxide, in the presence of a trace (0.01%) of sodium hydroxide catalyst, at 150160 C. and apressure of 10 pounds per square inch (gauge) for about 2 hours to effect completion of the condensationof the 2 mols of ethylene oxide with 1 molofthe amide.

Thesame procedure was repeated using 5 mols of ethylene oxide per mol of amide and the reaction required about 3 /2 hours to effect complete condensation.

Substantially the same results, as far as the condensation reaction is concerned, may be obtained using the above reaction conditions and using propylene oxide in-. stead of ethylene oxide and/or using other amidessuch as myristoyl diethanolamide, lauroyl.monoisopropanolamide, decanoyl dipropanol amide, dodecanoyl dibutanol amide, lauroyl dipentanol amide, myristoyl monoethanolamide, myristoyl monobutanol zamidezand so forth. The. number of mols (or the average number of mols) of alkylene oxide per mol ofamide may, of course, be varied through the range of about 2-5 mols. One of the most preferred amide condensates'for use herein is the condensate of about 1 mol of ethylene oxide with (1 mol of). lauroyl diethanolamide.

The addition of the aforementioned amide derivatives is particularly advantageous in the preparation of concentrated liquid detergents, since these particular amide derivatives impart unusually superior foam stability and foam endurance to the concentrated liquid detergent compositions. Accordingly, the addition of this amide derivative is useful not only for the purpose of eliminating the sulfate content of the sulfonate detergent, but also for the purpose of adding a desired additive for the detergent composition that will ultimately be prepared from these ingredients. Although the amide additive may be employed in quantities of as much as or even more than the weight of the sulfonate detergent, it is generally not necessary to employ more than about /2 of the weight of the detergent. Usually, at least an effective amount of about 5 weight percent of the detergent should be employed in order to obtain the advantages of the instant invention. Preferably, about 40 weight percent of the detergent is employed, and most preferably, about 25 weight percent ofthe detergent.

In the solvent system here employed, the proportions of the solvents used (as well as the particular solvents used) are determined by two considerations, namely, the amount of sulfate to be retained in solution and the ultimate solvent proportions desired in the filtered onephase system, which, in turn, is governed by the subsequent use contemplated. If a particular concentrated liquid detergent is to be made, then those solvents to be used as the selective solvent (in the volume ratio desired) should be used, if possible. The non-ionic derivative also contributes materially to the overall solubility of the system for the sulfate, and the amount of nonionic amide derivative to be used should also be considered in determining the specific solvent system to be used.

Most preferably, an ethanol-Water mixture is used, since ethanol is the ideal organic solvent for liquid detergents, having no characteristic odor or other features which might limit its use in such compositions. Also, it appears that the most effective coagulation results are obtained using the ethanol-water system. In general, the ethanol:wa-ter volume ratio should be 50:50 to 60:40, and most preferably, it is 59:41, which has been found to effectively eliminate all residual sulfate.

Actually, the ethanol:water volume ratio may be adjusted to the range of, for example, 3:5 to 4:1 to suit particular circumstances. At the lower ethanol:water volume ratios, such as 3:5, the combined effect of the solvent plus the amide derivative is ordinarily effective only to reduce the sulfate content partially, for example, to a content of about 1-5 weight percent, instead of completely eliminating the sulfate content. In general, it is desirable to reduce the sulfate content to less than about 1 weight percent of the composition (or less than about 2 weight percent of the sulfonate detergent), and for this purpose, the instant invention is particularly advantageous because it affords a method for reducing the sulfate content to within the range of 01%. By 0% is meant no detectable amount by ordinary analytical methods.

Although we have emphasized the use of ethanol in our process, as the preferred organic solvent, it should be understood that our invention also contemplates the use of other organic solvents. Such solvents include particularly the water-miscible alcohols (e. g. methanol and propanol), ketones (e. g. acetone), esters (e. g. methyl formate), and ethers (e. g. dimethyl ether). As will be appreciated the water-miscible organic solvents are capable of forming a one-phase solvent system with water, and each of the inorganic sulfates (e. g. Li, Na, K, NH4, etc. sulfates) is substantially insoluble in these organic solvents. Accordingly, if it is desired to obtain a solution containing x amount of sulfate (within the range of, for example, 0-1 part per parts of sulfonate), one selects a predetermined solvent system (with or without water) for admixture with the sulfonate and with the amide additive so that the resulting one-phase (sulfonate-amide-solvent system) will have a total sulfate solubility of 0-1 part. In so selecting the system to be used, the amount of solvent as well as the amount of amide to be used may also be considered since the crude sulfonate may be admixed with from about Me to about 5 times its weight of the solvent, if desired, and the amide may be added preferably in amounts of 550 weight percent of the detergent.

Another particularly advantageous aspect of the instant invention resides in the fact that it is not necessary to use water in the solvent system. In other words, the solvent system employed may be substantially anhydrous if desired, and in many instances, this is particularly advantageous. On the other hand, it will also be understood that the instant invention does not preclude the use of water-immiscible solvents, since these solvents may be used to particular advantage in an anhydrous system, and they may also be used in a one-phase solvent system with Water, if a suitable water-miscible solvent is also used. For example, if it is desired to use butanol (which is only about 9% soluble in water), it would be necessary to use an aqueous solvent system such as a waterzpropanol:butan0l system of perhaps 70:15:15 volume ratio in order to obtain a suitable one-phase system.

It will thus be seen that the selection of the solvent system to be used may be made from a variety of compounds and proportions, in the light of the present teachings, so as to obtain a number of different predetermined results in connection with sulfate elimination as well as in connection with the final compounding of a detergent composition.

After the sulfonated detergent has been neutralized by an inorganic base (which might be a carbonate or other basic compound instead of the hydroxide) the inorganic salt of the sulfonated detergent containing the residual inorganic sulfate has been admixed with the selected solvent system, at the neutralization temperature below, it will be noted that no appreciable coagulation or precipitation can be observed. On the other hand, if the amide additive is also incorporated in the detergent-solvent mixture, there is no appreciable immediate effect; but upon prolonged contact (preferably with agitation) an initial cloudiness appears and finally an effective coagulation of undesired sulfate particles takes place. The time of contact or agitation required to accomplish the dissolving of the detergent is, of course, relatively short; whereas the time of contact required to effectively cause coagulation of the sulfate, so as to permit removal thereof by filtration, is substantially greater. In general, at least about /2 hour is required, but the exact time necessary is readily ascertainable from routine sampling of the material.

Heating of the admixture during such agitation, so as to heat the admixture above the temperatures ordinarily maintained during neutralization, is not necessary in order to effect suitable coagulation of the sulfate; but such heating has been found to accelerate the coagulation reaction to an appreciable extent. In order to obtain the benefit of such heating, the admixture should be heated to at least about F. but not appreciably in excess of the boiling temperature. Preferably, a temperature of about l75-195 F. is obtained, and most preferably a temperature of about F. is used.

Next, the mixture is filtered. Any type of filtration generally suitable for removing solids or the like impurities from a solvent system of this type may be used. Filter systems of the type used to purify lacquer solutions, liquid food products or the like materials having usually only small sized particles therein may be used. Actually, the coagulation step changes the sulfate from a finely disweeper 1-3 videdunfilterable stage (conceivably of the nature of the sol-gel water-glass systems) to a stage capable of filtration in standard filter equipment. Most preferably, a filter cloth with a precoat is used.

If heating of the mixture has been used to accelerate coagulation, it is preferable to maintain the mixture in such heated states during filtratidn in order {Obbtin maximum advantage from th'e heating of the mixture. On the other hand, as was mentioned previously, it is not necessary to heat the instant mixture 'in order "to obtain effective and suitably rapid coagulation. It should be mentioned, however, that unless the ethanol-Water volume ratio is at least 1:1, the rateof 'coa'gulation is quite slow.

The difficulty in this situation is probably not so much speed'of coagulation as 'thetendency of the water-to hold the sulfate in solution; hence, 'the'water in larger amounts carries out this additional (and undesirable) function of increasing-the solubility 'of the system for the sulfate and also reducing the coagulating effect 'of the system. It will also be appreciated that thereis an'additional advantage in the use of heat for coagulation and during filtration so as to obtain maximum sulfate particle removal, since the subsequent cooling of the mixture effectively de-coagulates any small sized particles which might possibly pass through a filter screen or cloth so that these latter particles cannot cause any cloudiness in the :filtered and cooled product.

Various tests of the final product indicate that this product is, in fact, a one-phase system having dissolved therein the sulfonate and a very minor amount of residual sulfate, in those instances in which an-yresidual sulfate is permitted to remain. If the solventsystem iscapable of dissolving a certain amount of sulfate, in the presence of the amide additive, then this small amount of sulfate may'be retained in the system in solutionybut, inthose instances in which the ethanol:water volume ratio is at least as great as 59:41, and atleast an efiective amount ofthe amide is employed, the sulfate removal is complete for all intents and purposes, and standard analyticaltests will reveal no sulfatepresent in the system.

It will, of course, be appreciated that, whatever solvent system is used, that solvent system must be :a selective solvent for'both the detergent and the nonioni'c amide primarily and, secondarily, it will possess poor-or no;-solubility for the inorganic sulfate. If a very-substantial amount of water is used with a minor amount of the organic solvent, the system will not be insoluble toward the inorganic sulfate and the instant invention cannot be practiced. If a slightly larger amount of organic solvent is used, such as an ethanol:water ratio of 3:5, then the coagulation process will take place veryslowly, even in the presence of substantial amounts of the-amide additive (such as about 25 weight percent of the detergent) and the initial phases of the coagulationprocess;willinvolve merely the appearance of undesirable cloudiness in the detergent composition. In fact, in order to effectively complete the coagulation, it may be necessary to apply heat as hereinbefore indicated. In any event, the coagulation process is extremely slow, and its initial phase involves the undesirable cloudiness or fogginess in the detergent solution. Accordingly, the liquid deterg'ent 'c'o'mpositions heretofore prepared which contained asthe 'principal detergent an inorganic base neutralized "sulfonate'd detergent were prepared usingver'y substantial t'quantities of water in the solvent system. The object being to'avoid even the slightestfogginess or blush in the liquid detergent solution. Because of the necessity ofusing such substantial quantities of water in these'deter'gen't solutions that contained inorganic base neutralized sulfon'ated detergents, the tendency in industry was toward the use of organic base neutralized sulfonate detergents in such concentrated liquid detergent compositions. The verysuperior solubility of organicsulfates, such as triethanolamine sulfates, in organic solvents, such as ethanol, makes it possible to use the triethanolamine sulfonated'deter'gents 1-4 in concentrated solutions "having a desired rather high concentration of organic solvent.

The instant-invention, of course, avoids the use of high water concentrations in the solvent system. It does not preclude theme of these high water concentrations, since the water "could be added after coagulation has taken placerbut it also does not compel the use of high water concentrations in order to avoid fogginess in the concentrated'liquid detergents. Also, the instant invention avoids what was heretofore the practical necessity of using the relatively expensive ethanolamines as neutralizing agents for the 'sulfonated detergents, and it further avoid-s the additional expense of using such ethanolamines to neutralizethe sulfate impurities contained in the crude sulfonated detergent.

Still another aspect of the instant invention resides in an improved method for producing certain organic base neutralized sulfonateddetergents. As will be appreciated, the organic base sulfate salts are soluble in the organic solvents (such as ethanol) here employed and such sulfates may not be eliminated as the inorganic sulfates may. The organic bases are unusually the amine bases and 'thern'ost common of these are the alkylolamines, including monoalkylol, dialkylol, trialkylol, etc. amines, specific examples of which include monoethanol, diethanol,'ti'iethanol,.monopropanol, etc. amines. At present, the most.s'atisfactory commercially available alkylol amine aryl sulfonates arethe triethanolamine salts, which are considered superior to various other organic as well as inorganic base neutralized sulfonates of this class. One of the reasonsfor this alleged superiority is based upon the superior solubility of triethanolamine sulfonate, as compared 'to" the,inorganic sulfates. However, the presence of the triethanolamine sulfate is still not desirable; it is merely less undesirable.

Inour invention, we use as a neutralizing agent for the sulfonated detergent an ammonium base such as ammonia or ammonium hydroxide so as to obtain a composition consisting essentially of ammonium salt of the sulfonated'detergen-t, as for example, by substituting ammonia for the sodium hydroxide used in the demonstration hereinbefore described so as to obtain a composition of ammonium dodecyl benzene sulfonate containing about l0'%'ammonium sulfate. (The ammoni-' um cation has'less molecular Weight than the sodium cation.) We may then 'use substantially an equal Weight of ethanol and carry out the mixing (and heating, if preferred) and filteringas described so as to obtain a one-phase system which contains no analytically detectableamount of sulfate. Anhydrous alcohol (ali-canol) is preferably used with the ammonium salt (most preferably anhydrousethanol) Next, We'add to this system, a small amount of triethanolamine (so as to insure maintenance of an alkaline pH during the subsequent reaction) and we react the ammonium dodecyl benzene sulfonate therein with a suitable C2-C3 alkylene oxide such as ethylene or pro-- pylene oxide. The ethylene oxide combines at a ratio of 3 mols to 1 of the sulfonate so as to form triethanob amine dodecyl benzene sulfonate. The reaction of thylene-dxi'de -With'an ammonium salt is Well known and need not be detailed herein. The ingredients are preferably enclosed in a'vessel and the ethylene oxide is added thereto 'with agitation under a slight pressure of 10 pounds per square inch (gauge) and at a temperature of to 200' F. Other known amine addition reactions maybe employed 'to obtain other amine salts of the detergent, as long as these reactions, like the ethylene oxidemeaction, are not interfered with by the presence of the instant amide additive.

Comparable results may, of course, be obtained using, in the place of the lauroyl diethanolamide, others of the non-ionic. amide derivatives herein disclosed. Such compounds include among the dialakylolamides: caproyl clie'thanolamide, N,N bis'(2j3 dihydroxy propyl) myristamide, and myristoyl diethanolamide; most preferably the acyl group is saturated and is a Crz-Cm group. Such compounds also include among the polyalkoxyalkylolamides: diethoxyisopropanolamide and pentaethoxyisopropanolamide of lauric acid, diethoxy diethanolamide of lauric and of myristic acids, etc.; most preferably the acyl group is saturated and is a C12-C14 group. Each of such nonionics apparently cooperates with the anionic sulfonate in a unique manner, so as to effect complete inorganic sulfate coagulation and removal in the presence of 59:41 volume ratio ethanolzwater in the manner described, and to bring about theother results described using other solvent volume ratios.

Comparable results to those obtained using a sodium base neutralization may also be obtained using other metal bases, such as the lithium or potassium bases. Likewise, comparable results may be obtained using other sulfonated detergents such as fatty alcohol sulfonates, preferably C10C1s alkyl sulfonates such as decyl, lauryl, keryl, dodecyl, myristyl, tetradecyl, cetyl and hexadecyl sulfonates; and such as the Clo-C16 alkyl aryl hydrocarbons such as decylbenzene, laurylbenzene, kerylbenzene, tetradecylbenzene, myristylbenzene, and hexadecylbenzene sulfonates. 1

The term consisting essentially of as used herein to define the ingredients present in the claimed composition is intended to exclude the presence of other materials in such amounts as to interfere substantially with the properties and characteristics possessed by the claimed composition but to permit the presence of other materials in such amounts as not to affect substantially said properties and characteristics adversely.

Alterations and modifications may be made in the formulations herein without departing from the scope of the present invention.

-We claim as our invention:

1. A method of treating a composition comprising essentially water-soluble alkyl aryl anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and 1 to 20 Weight percent thereof of alkali metal sulfate salt, that comprises intimately admixing the composition with substantially an equal weight of ethanol and water in volume ratio of 59:41 and with -50 weight percent of amide derivative selected from the group consisting of (l) dialkylolamide having the formula:.

RI RCO-N/ wherein RCO is a fatty acyl radical of to 14 carbon atoms, and R and R" are hydroxyalkyl groups of up to 5 carbon atoms each; and (2) polyalkoxyalkylolamide condensate of 2 to 5 mols of alkylene oxide having 2 to 3 carbon atoms with 1 mol of higher fatty acid amide having the formula:

A! RCON/ All wherein RCO is a fatty acyl radical of 10 to 14 carbon atoms, and A and A are each selected from the group consisting of H and hydroxyalkyl radicals of up to 5 carbon atoms each and each having 1 to 2 hydroxy groups with none of the carbon atoms having more than one hydroxy group attached thereto; agitating for at least one-half hour to effect coagulation of the sulfate salt particles therein, and then filtering the admixture to remove the coagulated salt particles therein.

2. A method of treating a composition comprising essentially water-soluble alkyl aryl anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and l to 20 weight percent thereof of alkali metal sulfate salt, that comprises intimately admixing the composition with substantially an equal weight of ethanol,

and water n vo u e r t p oi 9s0 t9 6 49 n w h 10-40 Weight percent of dialkylolamide having the formula: t

wherein,R-CO- is a fatty acyl radical of 10 to 14 carbon atoms, and R and R" are hydroxyalkyl groups of up to 5 carbon atoms each; agitating for a time sufficient to completely dissolve the sulfonated detergent and to effectively coagulate the undissolved sulfate salt particles therein, and then filtering the admixture to remove the coagulatedsalt particles therein.

3. A method of treating a composition comprising essentially water-soluble alkyl aryl anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and 1 to 20 weight percent thereof of alkali metal sulfate salt, that comprises intimately admixing the composition with substantiallyan equal weight of ethanol and water in volume ratio of 50:50 to 60:40 and 25% of dialkylolamide having the formula:

wherein RCO is a fatty acyl radical of 10 to 14 carbon atoms, and R and R" are hydroxy alkyl groups of up to 5 carbon atoms each; heating the admixture to from 135 F. to boiling temperature for a time sufficient to completely dissolve the sulfonated detergent and to effectively coagulate the undissolved sulfate salt particles therein, and then filtering the admixture to remove the coagulated'salt particles therein.

. 4. A method of treating a composition comprising essentially parts of water-soluble alkyl aryl anionic sulfonated detergent having a long aliphatic chain of 8 to 22 carbon atoms, and 1 to 20 parts of inorganic sulfate salt of the class consisting of ammonium, alkali metal and alkaline earth metal sulfates whereby the amount of inorganic sulfate salt therein may be reduced to a predetermined amount, within the range of 0-1 part, which comprises intimately admixing the composition with 5-50 weight percent of amide derivative selected from the group consisting of (1) dialkylolamide having the formula:

RC ON/ wherein RCO is a fatty acyl radical of 10 to 14 carbon atoms, and R and R" are hydroxyalkyl groups of up to 5 carbon atoms each; and (2) polyalkoxyalkylolamide condensate of 2 to 5 mols of alkylene oxide having 2 to 3 carbon'atoms with 1 mol of higher fatty acid amide having the formula:

wherein RC0 is a fatty acyl radical of 10 to 14 carbon atoms, and A and A" are each selected from the group consisting of H and hydroxyalkyl radicals of up to 5 carbon atoms each and each having 1 to 2 hydroxy groups with. none of the carbon atoms having more than one hydroxy group attached thereto; and /2 to 5 times its weight of a one phase solvent system of water admixed with low molecular weight solvents of the class consisting of alcohols, ketones, esters and ethers in an amount sufficient to reduce the total solubility of the system for the inorganic sulfate salt to said predetermined amount, then agitating the admixture at a temperature of from F. to boiling and for a time sufiicient to completely dissolve the sulfonated detergent and to effectively coagulate the undissolved inorganic sulfate salt particles 17 therein, and then filtering the admixture to remove the coagulated salt particles therein.

5. A method as claimed in claim 4 wherein the solvent system consists essentially of water and alkanol having 2 to 3 carbon atoms.

6. A method as claimed in claim 5 wherein the alkanol is ethanol.

7. A method as claimed in claim 6 wherein the detergent is sodium dodecylbenzene sulfonate and the inorganic sulfate salt is sodium sulfate.

8. A method as claimed in claim 4 wherein the detergent is a salt of higher alkyl mononuclear aryl sulfonate detergent, said higher alkyl group having 8 to 22 carbon atoms.

9. A method as claimed in claim 8 wherein the detergent and the inorganic salt are both salts of an alkali metal.

10. A method as claimed in claim 4 wherein the detergent and the inorganic salt are both ammonium salts, and the solvent system is replaced by anhydrous alkanol.

11. A method as claimed in claim 10 wherein the amide derivative is lauroyl diethanolamide.

12. A method as claimed in claim 4 wherein the amide derivative is a C12-C14 fatty acyl diethanolamide,

13. A method of preparing a detergent, that comprises sulfonating dodecylbenzene by reaction therewith of a suitable excess of a sulfonating agent and then washing the reaction product to obtain a composition consisting essentially of dodecylbenzene sulfonic acid and residual sulfonating agent, neutralizing the composition with a sodium base to obtain a composition consisting essentially of sodium dodecylbenzcne sulfonate and sodium sulfate salt in residual amounts, then admixing the neutralized composition with substantially an equal weight of ethanol and water in volume ratio of 59:41 and l40 weight percent of polyalkoxyalkylolamide condensate of 2 to mols of alkylene oxide having 2 to 3 carbon atoms with 1 mol of higher fatty acid amide having the formula:

All

wherein RCO- is a fatty acyl radical of to 14 carbon atoms, and A and A" are each selected from the group consisting of H and hydroxyalkyl radicals of up to 5 carbon atoms each and each having 1 to 2 hydroxy groups with none of the carbon atoms having more than one hydroxy group attached thereto; maintaining the admixture at 185 F. for at least one-half hour to effect coagulation of the inorganic sulfate salt particles therein, and then filtering the admixture to remove the coagulated salt particles therein.

'18 14. A method of preparing a detergent, that comprises sulfonating dodecylbenzene by reaction therewith of a suitable excess of a sulfonaiing agent of the class consisting of concentrated sulfuric acid, chlorosulfonic acid and sulphur trioxide, under substantially anhydrous conditions, and then washing the reaction product to obtain a composition consisting essentially of dodecylbenzene sulfonic acid and residual sulfonating agent, neutralizing the composition with a sodium base to obtain a composition consisting essentially of sodium dodecylbenzene sulfonate sodium sulfate salt in residual amounts, then admixing the neutralized composition with substantially an equal weight of ethanol and water in volume ratio of 50:50 to :40 and 10-40 weight percent of dialkylolamide having the formula:

RI RC ON/ wherein R-CO is a fatty acyl radical of 10 to 14 carbon atoms, and R and R" are hydroxyalkyl groups of up to 5 carbon atoms each; agitating for a time willcient to completely dissolve the sulfonated detergent and to effectively coagulate the undissolved sodium sulfate salt particles therein, and then filtering the admixture to remove the coagulated salt particles therein.

15. A method of preparing high purity triethanolamine dodecyl benzene sulfonate, that comprises sulfonating dodecyl benzene by reaction therewith of a suitable excess of a sulfonating agent and then washing the product to obtain a composition consisting essentially of dodecylbenzene sulfonic acid and residual sulfonating agent, neutralizing the composition with an ammonium base to obtain a composition consisting essentially of ammonium dodecyl benzene sulfonate and ammonium sulfate in residual amounts, then admixing the neutralized composition with 25 weight percent thereof of lauroyl diethanolamide and susbtantially an equal weight of ethanol, agitating the admixture for a time sufiicient to completely dissolve the sulfonate and to effectively coagulate the undissolved sulfate, filtering to remove such coagulated undissolved sulfate, and then treating the filtered composition With ethylene oxide to convert said ammonium sulfonate to triethanolamine dodecyl benzene sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS 2,244,512 Brandt June 3, 1941 2,247,365 Flett July 1, 1941 2,316,719 Russell Apr. 13, 1943 2,477,383 Lewis July 26, 1949 2,607,740 Vitale Aug. 19, 1952 

1. A METHOD OF TREATING A COMPOSITION COMPRISING ESSENTIALLY WATER-SOLUBLE ALKYL ARYL ANIONIC SULFONATED DETERGENT HAVING A LONG ALIPHATIC CHAIN OF 8 TO 22 CARBON ATOMS, AND 1 TO 20 WEIGHT PERCENT THEREOF OF ALKALI METAL SULFATE SALT, THAT COMPRISES INTIMATELY ADMIXING THE COMPOSITION WITH SUBSTANTIALLY AN EQUAL WEIGHT OF ETHANOL AND WATER IN VOLUME RATIO OF 59:41 AND WITH 5-50 WEIGHT PERCENT OF AMIDE DERIVATIVE SELECTED FROM THE GROUP CONSISTING OF (1) DIALKYLOLAMIDE HAVING THE FORMULA: 